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                    <h1>QT基础6——基础绘图</h1>
                    
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                <h4 id="1、重写绘图事件"><a href="#1、重写绘图事件" class="headerlink" title="1、重写绘图事件"></a>1、重写绘图事件</h4><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br></pre></td><td class="code"><pre><span class="line">.h文件</span><br><span class="line">protected:</span><br><span class="line">    //1、重写绘图事件，虚函数</span><br><span class="line">    //2、如果在窗口绘图，必须放在绘图事件里实现</span><br><span class="line">    //3、绘图事件内部自动调用，窗口需要重绘的时候（状态改变，如缩放、鼠标点击之类）</span><br><span class="line">    void paintEvent(QPaintEvent *);</span><br></pre></td></tr></table></figure>
<h4 id="2、绘图事件中调用相关函数"><a href="#2、绘图事件中调用相关函数" class="headerlink" title="2、绘图事件中调用相关函数"></a>2、绘图事件中调用相关函数</h4><p>绘图功能需要用到QPainter对象，QPainter有两种创建方式</p>
<ul>
<li><p>QPainter(QPaintDevice *device)，QWidget继承于QObject和QPaintDevice 所以所有视图均为QPaintDevice子类，可以写为QPainter p(this);</p>
</li>
<li><p>QPainter p1;绘图代码写于p1.begin(this);和p1.end();之间</p>
</li>
</ul>
<figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br><span class="line">38</span><br><span class="line">39</span><br><span class="line">40</span><br><span class="line">41</span><br><span class="line">42</span><br><span class="line">43</span><br><span class="line">44</span><br><span class="line">45</span><br></pre></td><td class="code"><pre><span class="line">void Widget::paintEvent(QPaintEvent *)</span><br><span class="line">&#123;</span><br><span class="line">    //QPaintDevice,widget多继承于QObject和QPaintDevice</span><br><span class="line">    QPainter p(this);</span><br><span class="line"></span><br><span class="line">    //创建画图对象</span><br><span class="line">    //指定绘图对象的绘图设备</span><br><span class="line">//    QPainter p1;</span><br><span class="line">//    p1.begin(this);</span><br><span class="line"></span><br><span class="line">	//画图片</span><br><span class="line">//    p.drawPixmap(0, 0, width(), height(), QPixmap(&quot;../Image/bg.png&quot;));</span><br><span class="line"></span><br><span class="line">    //绘笔</span><br><span class="line">    QPen pen;</span><br><span class="line">    //设置常用颜色</span><br><span class="line">//    pen.setColor(Qt::red);</span><br><span class="line">	//	设置线宽</span><br><span class="line">    pen.setWidth(5);</span><br><span class="line">    //以rgba设置颜色</span><br><span class="line">    pen.setColor(QColor(12, 34, 255, 255));</span><br><span class="line">    //设置绘笔风格</span><br><span class="line">    pen.setStyle(Qt::DashDotLine);</span><br><span class="line">	</span><br><span class="line">    //将绘笔赋予painter</span><br><span class="line">    p.setPen(pen);</span><br><span class="line">    //画线</span><br><span class="line">    p.drawLine(50, 50, 50, 150);</span><br><span class="line">    //画矩形</span><br><span class="line">    p.drawRect(20, 30, 110, 200);</span><br><span class="line">    //画椭圆</span><br><span class="line">	p.drawEllipse(QPoint(150, 150), 60, 100);</span><br><span class="line">    </span><br><span class="line">    //笔刷</span><br><span class="line">    QBrush  brush;</span><br><span class="line">    //设置常用颜色</span><br><span class="line">    brush.setColor(Qt::red);</span><br><span class="line">    //设置笔刷风格</span><br><span class="line">    brush.setStyle(Qt::Dense4Pattern);</span><br><span class="line">    //将笔刷赋予painter</span><br><span class="line">    p.setBrush(brush);</span><br><span class="line">    p.drawEllipse(QPoint(150, 150), 60, 100);</span><br><span class="line"></span><br><span class="line">//    p1.end();</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure>

                
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